Electric iron



Sept. 17, 1929. F. F. FQRSHEE ET AL ,7

ELECTRIC IRON Original Filed Dec. 29, 1925 2 Sheets-Sheet 1 INVENTORS.

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I ATTORNEY Sept. 17, 1929.

F. F. FORSHEE ET AL I 1,728,791

ELECTRIC IRON Original Filed Dec. 29, 1925 2 Sheets-Sheet 2 WITNESSES FgjgNTOZS. &

- ran on? 66 @141- A Y Fran/1 777007/0/7. & -.I. m/l/ 1' ATTORNEYPatented Sept 17, 1929 I NI ED STA Es PATENT OFFICE-- FRANK F. FORSHEEAND FRANK THORNTON, OF MANSFIELD, OHIO, ASSIGNORS TO .WESTINGHO'USEELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA ELECTRICIRON Application filed December 29, 1925, Serial No. 78,101. RenewedOctober 26, 1928.

Our invention relates to electric heating Fig. 1 is a view in verticalcross-section of devices and particularly to electrically heata -flatiron embodying our invention; ed flat irons. Fig. 2 is a side view of asupporting mem- An object ,of our invention is to-provide a her forterminal members and the thermallyflat iron that. shall have its heatingelement actuable switch employed in the device illus- 55 embedded initstop plate. I U r v trated in Fig.1;

;,Another object of our invention isto'pro- Fig. 3 is a plan view of thesupporting vide a flat iron that shall have associated memberillustrated in Fig. 2; therewith, a heatin unit which iseasily Fig. 4.is a plan view of the top/casting, manufactured, readi y located in itsoperaembodying our invention; 1 60 tive osi tion within the flat iron,and which Fig. 5 is a view in. vertical section taken on will ave longlife. H I the line VV of Fig.4; and

v Heretofore,.the usua heater employed in Fig. 6 is a view in verticalsection taken electrically heated flat irons comprised a on the lineVI-VI of Fig. 4.

strip of mica, around which "was wound a Referring more particularly toFig. 1, an 65 conductor of high resistancematerial. ,The electric fiatiron 11 comprises a body porresistor was disposed in a metallic sheathtion 12, a supporting member 13 and a cover from which it wassuitablyinsulated by member, 14. The cover member 1a is atstrips ofmica. Heat transfer from the tached to the body member 12 by a bolt 15heating elementto the sole plate of the flat and encloses the topportion of the body iron has been efiected by a pressure clamp or member12 and the supporting member 13 weight member that was secured above thetherein. I heating element. v 4 I g The body portion 12 comprises a soleplate With this type'of construction, the heat 16, and a top plate 17secured thereto by ing. elements were. subjected to very high bolts 18and 19, which extend through the temperatures because of therelativelylow top member 17 and into the sole plate 16,

. thermal conductivity of mica and the -reand nuts 18a and 20.

sultingf temperature drops between the ele- The sole plate 16 has apolished bottom I ment' and the mica and between the mica surface 21, abevelled edge 22 and a ground 30 and the sole plate. v top surface 23.Holes 24 and 25 are drilled In accordance with our invention, we haveand tapped in the sole plate 16 from the surprovided a heating unitwhich comprises an face 23 to receive bolts 18 and 19.

electric resistance conductor and an oxidiz- The top plate17 has anannular groove 28 able tube or sheath which encloses the conin thebottom surface thereof which makes 35 ductor'and is located in a castiron member. substantially a complete turn around its Bysubjecting thetube enclosing the resistor outer periphery and an opening 20 in itsrear to a gaseous atmosphere of suitable oxygen central portion whereinthe member 13 is content, the oxidizable metal ischanged to located. Aheating element 26 comprises an oxide thereof, and simultaneously exanelectric resistor 29 which is encased in a 0 pands sufiici'ently to,cause a compact and tube or helix 30 of oxidizable metal such asefficient heat path to exist between the elecmagnesium. The encasedresistor element 29 trical conductor andthe cast iron member. is locatedin the groove 28.

Since the resistor is in good 'thermal con- The top casting 17 with themagnesium tactwith the iron member, it will operate at metal tube 30,which encloses the resistor 4 a much'lower temperature than is the case29 located in the groove 27 is exposed to when the elements areinsulated by mica; steam at a high pressure accordlng to the therefore,the heating element will, under method described in United StatesLetters reasonable circumstances, have much longer Patent No. 1,451,755,lssued to O. B. Backer life than mica insulated elements. on April 17,1923 whereby the magnesium 50 In the accompanying drawings, metal 30 ischanged to magnesium oxide.

The magnesium metal, as it is oxidized, expands substantially to 200%ofits original volume. The heating element is compacted by the resultingoxide, to efiect a high thermally-conductive relation between theconductor 29 and the top plate 17. The

magnesium oxide is of a crystalline structure which extends radiallyfrom the resistor 29, and provides an excellent heat path therefrom tothe base plate 24. By reason of the efiicient'thermally-conductive pathbetween the conductor 29 and the base plate 17, the resistor element 29may be operated at a much lower temperature because the temperaturegradients between the conductor 28, oxide 29 and the base plate 16 arematerially reduced.

ince the heating unit 26 is treated in its operative position within thetop plate 17, the base plate 16 may be polished and finished forassembly without marring the polished surface as would obviously resultif the heating element 26 were located in the base plate 16. Obviously,it would be very difficult to treat the magnesium oxide coveredconductor 29 in place in the base plate 16 before said base plate hasbeen nickel-plated or polished because of the damaging effect of theacid solutions employed in the electro-plating processes.

The ends of the resistor 29 are brought upwardly through openings 31 and32 in the top casting 17 illustrated in Fig. 4. One end of the resistor29, which passes through the opening 32, is connected to a terminal 33of a thermostat 34 which is supported by the member 13. From a secondterminal, not shown, of the thermostat 34 a connection is made toterminal 35. The other end of the resistor 29, which passes through theopening 31, is connected to a secondv terminal similar to terminal 35but which is not shown in the drawings.

The supporting member 13 is of substantially L-shape, and serves as asupport for the terminals 35, only one of which is shown, and alsoserves to support the thermostat 34 in its operative osition, asillustrated in Fig. 1.

Openings 3 and 38 are provided in a short leg 39 of the member 13,wherein the terminals 35 are supported andheld firmly in position by acircular integral lug 41 on the terminals 35 and nuts 40. The terminalsare insulated from the member 13 by insulating washers a of mica. Anopening 42 is provided in the member 13 to permit the bolt 19 to passtherethrough. The member 13 is held firmly in place by the bolt 19 and anut 20. The thermostat 34 is supported from the member 13 by a bolt 43located in an opening 44 thereof, and secured thereto by a washer 46 anda nut 47. A pair of openings 48 and 49 are provided in the member 13whereby the terminals 33 of the thermostat 34 may be 10- catedinposition in order that the resistor 29 heating means,

may be connected thereto. A depending lug 50 of the L-shape member 13prevents sai member from bending downwardly so that the thermostat 34will not touch the sole plate 16.

A thermally responsive member 51 of the thermostat 34 is located nearestthe sole plate 16 in order that it may be subjected to substantially thetemperature existing at the surface 21 of said sole plate. Thesupporting member 13 is secured to the top plate 24 by the bolt 19.

The thermostat 34 which we propose to use is described in U. S. LettersPatent No. 1,448,240 issued to J. A. Spencer on March 13,1923.

The cover member 14, as illustrated in Fig. 1, has a handle portion 52attached thereto by supporting straps 53 and 54. The straps 53 and 54are secured to the handle by bolts, not shown, and to the cover 14 byrivets 55 and 56. An opening in the rear portion of the cover member 14permits the terminals 35 to extend outwardly therefrom, whereby anelectrical connection may be effected to an electric power supply.

y means of our invention, we have provided an electrically heated ironwhich comprises a sole plate, that ma be finished and polishedindependently of the heating unit, a means for heating the aforesaidsole plate, a thermally-actuable switch for controlling the temperatureof the sole plate, and a cover member for enclosing the body portion,the and the thermally-actuable switch. The heating means comprisessubstantially a cast iron member having a groove in its lower surfacewherein a heating element is located and insulated therefrom by anoxidizable material such as magnesium.

The heating means provided in the device embodying our invention may betreated in an autoclave as described in the United States Letters PatentNo. 1,451,755 issued to G. B. Backer on April 17 1923. Since the heatingmember is treated independently of the sole plate and since the heatingunit lends itself to quantit production, we have provided an iron whicmay be easily repaired or easily assembled, as the case may be, becauseof the simplicity of the heating unit.

Obviously other modifications and changes in the device illustrated inthe drawings embodying our invention may be made without departing fromthe spirit and scope thereof.

We therefore desire that only such limitations shall be placed thereonas shall be imposed by the prior art.

We claim as our invention:

In an electrically heated iron, the combination with a body portioncomprising a. top castin having a groove therein, a sole plate, aheating element located in the groove in said top casting, terminal pinsfor the heating element, and a thermally actuable control switch insurerigggcribed our names this27th day of Nov.

' FRANK F. FORSHEE.

mum; THORNTON.

